Posted on 16 July 2019

Power Conversion Standard Sets Direction for Suppliers and OEMs




By Tom Newton, IPC Director of PCB Programs, Standards and Technology


Power conversion devices (PCDs) are used throughout the computer and telecommunications industries; however, until now, there was no defined standard for these devices. A standard was needed to improve field performance of power conversion devices, reduce the overall qualification interval for these devices and provide customer requirements for consumer and telecommunications grade PCDs. As a result, IPC — Association Connecting Electronics Industries® published the first-ever power conversion standard, IPC-9592, Requirements for Power Conversion Devices for the Computer and Telecommunications Industries, in September 2008.

The standard was developed by the Power Conversion Devices Standard Subcommittee (9-82) of the IPC OEM Management Council Steering Committee (9-80). It comprises representatives from leading original equipment manufacturers (OEMs) and power conversion equipment suppliers, such as Alcatel- Lucent, Cisco Systems, Dell Inc., Emerson Network Power, Hewlett-Packard Co., IBM, Lineage Power, and Murata Power Solutions.

IPC-9592 details what is required as far as the mechanical, electrical, environmental, quality- and reliability-assurance, and regulatory aspects of power conversion are concerned.

For mechanical, that includes form and size, connector and wiring configurations, and cooling needs. The electrical standards focus on interface specifics, including power source, input voltage, frequency and current needs, output voltage and, when applicable, logic controls. The environmental standards identify operating and shipping temperatures, humidity, shock and vibration limits. The quality/reliability standards include definitions and requirements for the design and testing of power conversion devices, and the regulatory portions of the document spell out international standards for safety, electronic interference and environmental impact of power-conversion devices.

The standard refers to three categories of power conversion devices (PCDs): Category 1: dc output power supplies to be embedded in equipment, whether the input power is acac or dc. Category 2: Board mounted dc-to-dc converters including both isolated and non-isolated converters Category 3: ac-to-dc power supplies used as adapters and chargers that are external to the equipment being powered.

Product specifications and documentation requirements should follow a specific set of guidelines and appear in a delineated format. Such documentation includes the theory of operation; applicable schematics; qualification test plan; reports for electromagnetic compatibility (EMC), sample qualification tests, design verification testing (DVT), highly accelerated life testing (HALT), SMT power module solder attachment reliability, and derating; reliability data and calculation; design checklist; failure mode and effect analysis (FMEA) for custom products; bill of materials (BOM); approved supplier list for all components; PCB artwork; component drawings, including magnetic; manufacturing drawings; regulatory reports (if applicable); change history; and mechanical dimension measurements.

The data sheet should provide complete specifications of form, fit and function, including electrical specifications and whether it is a Class 1, general or standard PCD, or Class 2, enhanced or dedicated service PCD. The date and revision level should be marked at the bottom of the sheets. Items to be addressed are input power logic, indicator, control, and output specifications; reliability, safety, and regulatory factors; physical dimensions and electrical specifications and requirements; and material control and labeling. In addition, the PCD supplier needs to implement a documented, capable material control system for all incoming, in-process, and outgoing materials and make available documentation of a material control plan.

Design for reliability means that industry best practices to specify, design, and document PCD performance and reliability are in place. Expected reliability of a PCD and the conditions under which the reliability is specified should be defined by the supplier and the user’s operating specifications provided. A documented process must be in place to select all components for product designs including information on all components and all component suppliers. IPC-9592 defines the factors that should be incorporated into the component selection process.

An important part of IPC-9592 involves derating documentation requirements and setting derating guidelines. To provide a reliable power conversion product, the standard document sets forth a method of component derating to use in all electrical designs. It provides details on the derating methods, conditions and results. Derating is a technique used to ensure that component ratings are not exceeded, either under steady state or transient conditions. The intent of component derating is to improve reliability of electrical components in electronic products by compensating for many variables inherent in a design. Proper component derating will lower failure rates through reduced stresses; reduce the impact of material, manufacturing, and operational variability; and enable continued circuit operation with long-term part parameter shifts.

When there is a custom PCD design on new topologies or architectures with no previous design failure modes and effects analysis (DFMEA), or in cases where there are new technology components, the supplier should provide a DFMEA to the customer with results of the analysis and of any corrective actions. DFMEA is to be performed early in the power supply development cycle. DFMEA activities are designed with three aims: to recognize and evaluate the potential failure modes of each component in a product and its effects on the product, to identify actions that could eliminate or reduce the chance of the potential failure occurring and to document the process for improvement of future designs.

Design and qualification testing is a central and detailed focus of IPC-9592. The testing described has two main purposes. First, design verification testing and electromagnetic susceptibility testing, including electromagnetic interference (EMI) and electrostatic discharge (ESD) testing, are intended to provide assurance that the device will function according to its specification. Second, environmental stress testing, including HALT, is intended to provide a measure of assurance (not proof) that the device is robust enough to operate in its intended environment without damage or degradation that would affect its operation.

There was such urgency for the document’s original release in September 2008, as its core features were just in place, that work on its revision A was in progress even before the original standard was in print. Under the leadership of the 9-82 Subcommittee’s new chair, Neil J. Witkowski of Alcatel-Lucent, the committee expects the new revision to be published by the end of 2009. The revision will include significant additions to the document’s portions dealing with corrosion of a power conversion/power supply unit in the field, more definitive information of highly accelerated life testing (HALT), moisture sensitivity levels (MSL) of the devices and components and proper preconditioning of the devices or modules for testing.

Copies of IPC-9592 can be purchased through Call IPC customer service for more information at +1 847-597-2862.





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